I've given this one a fair bit of thought before now, actually.
I think if I could choose, and afford it, I'd hire someone to monitor my life and generate a random. The random would be when they killed me. I'd instruct them never to interfere with my life, only to be aware of my every move, so that they could end me at any time. I don't care how they choose the random (when to end me); it could be when they feel like it, or based on the value of pi, I just don't want to know. They could follow me about in person, physically, or they could never see me again until the day it was time. I just don't want to know.
I think I'd live my life much better if I knew that there was someone out there who was, without doubt, going to kill me, and I had no idea when.
As for the precise means, I guess that'd be up to them, though I would have a few stipulations. It would have to be fast, I think. I've seen some weapons fire in real life, and I reckon the speed at which my head would implode following the impact of certain bullets would be faster than the speed of neural transmission, and so complete as to rule out any partial transmissions in the aftermath. It'd have to be a high velocity, high caliber job though. It would have to end immediately, and with no warning.
Unfortunately, I don't presently have the resources to arrange such a set-up. I plan to accumulate. =)